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Bahan kajian pada MK Pertanian Berlanjut Diabstraksikan oleh: smno.jursntnh.fpub. okt 2012 HIDROLOGI LANSEKAP DAN RAINWATER HARVESTING.

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Presentasi berjudul: "Bahan kajian pada MK Pertanian Berlanjut Diabstraksikan oleh: smno.jursntnh.fpub. okt 2012 HIDROLOGI LANSEKAP DAN RAINWATER HARVESTING."— Transcript presentasi:

1 Bahan kajian pada MK Pertanian Berlanjut Diabstraksikan oleh: smno.jursntnh.fpub. okt 2012 HIDROLOGI LANSEKAP DAN RAINWATER HARVESTING

2 Diunduh dari Sumber: 17/10/2012 HIDROLOGI…. “HIDROLOGI” …. Kajian ilmiah tentang sifat-sifat, distribusi dan efek-efek air di permukaan bumi, di dalam tubuh tanah, di dalam batuan bawah tanah, serta air di atmosfir. ….. Siklus Hidrologi

3 Diunduh dari Sumber: 17/10/2012 PENTINGNYA VEGETASI POHON DALAM SIKLUS HIDROLOGI…. Aliran air dalam siklus hidrologi: (1)Evaporasi air dari permukaan; (2)Transpirasi oleh tumbuhan; (3)Transport air di atmosfir; (4) Presipitasi (Hujan); (5) Limpasan permukaan (runoff) dan aliran bawah permukaan.

4 Diunduh dari Sumber: 17/10/2012 NERACA AIR DAN NERACA ENERGI …. POHON…. Precipitation (P) is any and all forms of water that fall from clouds and reach the ground. Runoff (R) is the water from precipitation that is not absorbed into the soil, but flows and reaches a stream or another body of water. Evapotranspiration (E) is water evaporating from wet surfaces and the soil plus the water release of plants.

5 Diunduh dari Sumber: 17/10/2012 PENTINGNYA HUTAN DALAM SIKLUS HIDROLOGI…. Air hujan yang jatuh dari langit : Menguap kembali ke atmosfir, mengalir di permukaan lahan (runoff), meresap ke dalam tanah (infiltration).runoffinfiltration Proses-proses di atas dikendalikan oleh intensitas hujan, karakteristik tanah dan lahan, kemiringan lahan dan vegetasi.

6 Diunduh dari Sumber: 17/10/2012 DAERAH ALIRAN SUNGAI (DAS) …. WATERSHED DAS meliputi semua lahan yang menyalurkan air hujan memasuki suatu sistem sungai tertentu. DAS menangkap dan menyimpan air hujan, melepaskan air tersebut secara bertahap memasuki alur sungai. Perubahan dalam suatu DAS, secara alamiah atau buatan manusia, akan mempengaruhi kualitas air, kecepatan runoff, nilai habitat dan erosi, yang pada akhirnya akan berdampak pada keseluruhan DAS.

7 Diunduh dari Sumber: 17/10/2012 …NERACA AIR DI BENTANG LAHAN. Annual water balance for the Walnut Gulch Experimental Watershed. The Walnut Gulch Experimental Watershed is located primarily in a high foothill alluvial fan portion of the San Pedro River watershed. Cenozoic alluvium is very deep and is composed of coarse-grained fragmentary material, the origin of which is readily traceable to present-day mountain flanks on the watershed.

8 Diunduh dari Sumber: smno fpun… 17/10/2012 RAIN-WATER HARVESTING Panen air hujan merupakan suatu metode memanfaatkan air hujan untuk keperluan domestik dan pertanian, cara ini telah banyak diaplikasikan di berbagai penjuru dunia. DELAPAN PRINSIP KEBERHASILAN PANEN AIR HUJAN: 1.Mulai dari observasi lapangan dengan hati-hati dan kontinyu. 2.Mulai dari titik tertinggi drai bentang-lahan atau petakan lahan dan bekerja menuruni kemiringan lahan. 3.Mulai dari kerja kecil dan sederhana. 4.Memperlambat, menyalurkan dan menginfiltrasikan air hujan. 5.Merencanakan saluran pelimpas dan memanfaatkan air limpasan sebagai sumberdaya. 6.Memaksimumkan komponen organik /vegetatif dari tutupan lahan. 7.Memaksimumkan fungsi dan relasi-relasi yang baik dnegan jalan “stacking functions.” 8.Memonitor hasil kerja dan memperbaikinya terus menerus.

9 Diunduh dari Sumber: ….. 17/10/2012 RAIN GARDEN. “A rain garden” adalah sekungan di permukaan lahan yang ditanami (tumbuhan) yang memungkinkan air hujan yang mengalir dari lahan di sekitarnya ditampung dan diresapkan ke dalam tanah. Hal ini dapat mengurangi runoff air hujan dan memungkinkan air hujan meresap ke dalam tanah, sehingga dapat mengurangi ancaman erosi, pencemaran air, banjir dan kurangnya pasokan air ke dalam groundwater. “Rain garden’ ini dapat mengurangi pencemaran perairan dan sungai hingga sebesar 30%.

10 Diunduh dari Sumber: ….. 17/10/2012 CONTOH RAIN GARDEN….

11 Diunduh dari Sumber: ….. 17/10/2012 …EMBUNG PERTANIAN. Embung atau tandon air merupakan waduk berukuran mikro di lahan pertanian ( small farm reservoir) yang dibangun untuk menampung kelebihan air hujan di musim hujan. Air yang ditampung tersebut selanjutnya digunakan sebagai sumber irigasi suplementer untuk budidaya komoditas pertanian bernilai ekonomi tinggi di musim kemarau atau di saat curah hujan makin jarang. Embung merupakan salah satu teknik pemanenan air HUJAN yang sangat sesuai di segala jenis agroekosistem. Pembuatan embung untuk pertanian bertujuan antara lain untuk : 1.Menampung air hujan dan aliran permukaan ( run off) pada wilayah sekitarnya serta sumber air lainnya yang memungkinkan seperti mata air, parit, sungai- sungai kecil dan sebagainya. 2.Menyediakan sumber air sebagai suplesi irigasi di musim kemarau untuk tanaman palawija, hortikultura semusim, tanaman perkebunan semusim dan peternakan.

12 Diunduh dari Sumber: bebasbanjir2025.wordpress.com/.../embung/ ….. 17/10/2012bebasbanjir2025.wordpress.com/.../embung/. PERSYARATAN LOKASI EMBUNG…. 1.Daerah pertanian lahan kering/perkebunan/ peternakan yang memerlukan pasokan air dari embung sebagai suplesi air irigasi. 2.Air tanahnya sangat dalam. 3.Bukan lahan berpasir. 4.Terdapat sumber air yang dapat ditampung baik berupa air hujan, aliran permukaan dan mata air atau parit atau sungai kecil. 5.Wilayah sebelah atasnya mempunyai daerah tangkapan air atau wilayah yang mempunyai sumber air untuk dimasukkan ke embung, seperti mata air, sungai kecil atau parit dan lain sebagainya. Konstruksi pembangunan embung dapat dilakukan oleh kelompok tani secara padat karya dan bertahap.

13 Diunduh dari Sumber: 17/10/2012 INFILTRASI Some of the precipitation that falls on land seeps into the ground where it is stored in aquifers and is transported to streams and lakes by subsurface flow. The amount of infiltration is influenced by the permeability and moisture content of the soil, the presence of vegetation and the volume and intensity of precipitation. The amount of water in an aquifer is indicated by the height of the water table (the upper boundary of aquifer).

14 Diunduh dari Sumber: ….. 17/10/2012 INFILTRASI Infiltration is the downward movement of water from the land surface into the soil profile. 1.Infiltration. The downward entry of water into the immediate surface of soil or other materials. 2.Infiltration capacity. The maximum rate at which water can infiltrate into a soil under a given set of conditions. 3.Infiltration rate. The rate at which water penetrates the surface of the soil, expressed in cm/hr, mm/hr, or inches/hr. The rate of infiltration is limited by the capacity of the soil and the rate at which water is applied to the surface. This is a volume flux of water flowing into the profile per unit of soil surface area (expressed as velocity). 4.Percolation. Vertical and lateral movement of water through the soil by gravity.

15 Diunduh dari Sumber: ….. 17/10/2012 INFILTRASI Figure : Zones of the infiltration process for the water content profile under ponded conditions The distribution of water during the infiltration process under ponded conditions is illustrated in Figure. In this idealized profile for soil-water distribution for a homogeneous soil, five zones are illustrated for the infiltration process. Transmission zone. This zone is characterized by a small change in water content with depth. In general, the transmission zone is a lengthening unsaturated zone with uniform water content. Gravity forces primarily drive hydraulic gradient in this zone.

16 Diunduh dari Sumber: ….. 17/10/2012 INFILTRASI Soil-water infiltration is controlled by the rate and duration of water application, soil physical properties, slope, vegetation, and surface roughness. Generally, soil-water infiltration has a high rate in the beginning, decreases rapidly, and then slowly decreases until it approaches a constant rate. As shown in Figure, the infiltration rate will eventually become steady and approach the value of the saturated hydraulic conductivity. Source: Hillel, 1982 whenever water is ponded over the soil surface, the rate of infiltration exceeds the soil infiltration capacity.

17 Diunduh dari Sumber: ….. 17/10/2012 SISTEM INFILTRASI Surface infiltration can be achieved through the use of grass buffer strips, vegetated swales, and porous pavement systems. Infiltration systems such as infiltration trenches, infiltration basins, and bioretention areas (including rain gardens) are designed specifically to capture a defined volume of storm runoff and transfer it directly to the soil profile. Several integrated practices, such as soil quality restoration and native landscaping, can be used in conjunction with these practices to improve the infiltration capacity of compacted urban soils. An infiltration BMP is designed to capture a volume of stormwater runoff, retain it, and infiltrate all or part of that volume into the ground.

18 Infiltration hydraulics and process ….. A fundamental principle for describing the flow of water in a homogeneous, porous media is given by Darcy’s Law (Chow, Maidment, and Mays, 1988; McCuen, 1989): Q = KA  h/L where: Q = flow (cfsec); K = saturated hydraulic conductivity; characteristic of a specific porous medium when effectively saturated with water (fps); A = cross-sectional area through the porous medium perpendicular to the flow (ft 2 );  h/L = hydraulic gradient, the difference in hydraulic head,  h, per unit distance in the direction of flow, L ft/ft The velocity of flow through the porous medium can be determined from Equation 1 by substituting the continuity equation Q = qA to obtain: q = K (  h/L) where: q = velocity of water through a unit cross section of the porous medium (fps) The velocity of water through the pores of the medium is described by: V = q/  s where: V = fluid velocity (in/hr);  s = water content of the medium (in 3 /in 3 ) equal to the medium’s porosity less the volume of trapped air in the pore spaces. Diunduh dari Sumber: ….. 17/10/2012

19 Soils and infiltration …. Factors that control infiltration rate and capacity: 1.Vegetative cover, root development, and organic content 2.Moisture content 3.Soil structure and texture 4.Porosity and permeability 5.Soil bulk density and compaction 6.Slope, landscape position, and topography Diunduh dari Sumber: ….. 17/10/2012 Hydrologic soil group (HSG). The HSG refers to the soil characteristics that tend to decrease or increase the amount of runoff produced from a precipitation event. The HSG is used in the determination of the runoff curve number (CN) developed by the Natural Resource Conservation Service (NRCS). Group A. 1.Sand, loamy sand, or sandy loam soil types. 2.Low runoff potential and high infiltration rates, even when thoroughly wetted. 3.Includes deep and well- to excessively- drained sands and gravels. 4.High rate of water transmission (hydraulic conductivity). Group B. 1.Silt loam or loam. 2.Moderate infiltration rate when thoroughly wetted. 3.Includes moderately deep to deep, moderately well- to well-drained soils. 4.Moderately fine to moderately coarse textures.

20 Soils and infiltration …. Group C. 1.Sandy clay loam. 2.Low infiltration rates when thoroughly wetted. 3.Consists primarily of soils with a layer that impedes downward movement of water. 4.Moderately fine to fine structure. 5.Perched water table at inches; root-limiting at inches. Diunduh dari Sumber: ….. 17/10/2012 Group D. 1.Clay loam, silty clay loam, sandy clay, silty clay, and clay. 2.Very low infiltration rates when thoroughly wetted. 3.Consists chiefly of clay soils with high swelling potential, soils with a permanent high water table, soils with a claypan or clay layer at or near the surface, and shouldow soils over nearly impervious material. Soil texture. The hydrologic design methods presented are based on the use of two hydrologic soil properties; the effective water capacity (Cw) and the minimum infiltration rate (f) of the specific soil textural groups. Effective water capacity. The fraction of the void spaces available for water storage (in/in). Minimum infiltration rate. The final rate that water passes through the soil profile during saturated conditions (in/hr).

21 Hydrologic soil properties classified by soil texture Diunduh dari Sumber: ….. 17/10/2012 Soil texture classHydrologic soil group Effective water capacity (C w ) (in/in) Minimum infiltration rate (f) (in/hr) Effective porosity, θ e (in 3 /in 3 ) SandA ( ) Loamy sandA ( ) loamB ( ) LoamB **0.026 ( ) Silt loamC ( ) Sandy clay loamC ( ) Clay loamD ( ) Silty clay loamD ( ) clayD ( ) Silty clayD ( ) ClayD ( ) Note: Minimum rate: soils with lower rates should not be considered for infiltration BMPs

22 Screening criteria for infiltration practices …. Diunduh dari Sumber: ….. 17/10/2012 Evaluation of the viability of a particular site includes: Determine soil type from mapping and soil survey to review other parameters such as the amount of silt and clay, presence of a restrictive layer or seasonal high water table, and estimated permeability. The soil should not have more than 30 percent clay or more than 40 percent clay and silt combined. Eliminate sites that are clearly unsuitable for infiltration. If the surface and underlying soils are Group D or the saturated infiltration rate is less than 0.52 in/hr, the site should not be used for infiltration. Groundwater separation should be at least 4 feet from the basin invert to the measured groundwater elevation. Seasonal high groundwater should be a minimum of 4 feet below the infiltration surface. Bedrock or impervious soils should be a minimum of 4 feet from the infiltrating surface (i.e. bottom of trench). Location should be the following distances away from structures: 1). Buildings, slopes, and highway pavement: greater than 25 feet 2). Wells and bridge structures: greater than 100 feet. Infiltration practices should not be placed in locations that cause water problems to downgrade properties. Infiltration facilities should be set back 25 feet (10 feet for dry wells) down-gradient from structures.

23 Point system for the evaluation of potential infiltration sites Diunduh dari Sumber: ….. 17/10/2012 1Ratio between tributary-connected impervious area (A IMP ) and the infiltration area (A INF ): A INF > 2 A IMP 20 points A IMP ≤ A INF ≤ 2 A IMP 10 points 0.5 A IMP ≤ A INF ≤ A IMP 5 points Urban catchments with pervious surfaces smaller than 0.5 A IMP should not be used for infiltration. 2Nature of surface soil layer: Coarse soils with low ratio of organic material7 points Normal humus soil5 points Fine grained soils with high ratio of organic material0 points 3Underlying soils: If the underlying soils are coarser than surface soils, assign the same number of points as for the surface layer under criterion #2. If the underlying soils are finer-grained than the surface soils, use the following points: Ø Gravel, sand, or glacial till with gravel or sand7 points Ø Silty sand or loam5 points Ø Fine silt or clay0 points

24 Point system for the evaluation of potential infiltration sites Diunduh dari Sumber: ….. 17/10/2012 4Slope (S) of the infiltration surface: · S < 7%5 points · 7% ≤ S ≤ 20%3 points · S > 20%0 points 5Vegetation cover: · Healthy, natural vegetation cover5 points · Lawn – well established3 points · Lawn – new0 points · No vegetation – bare ground-5 points 6Degree of traffic on infiltration surface: · Little foot traffic5 points · Average foot traffic3 points · High foot traffic (i.e. playing/sports fields)0 points Source: Adapted from Urbonas and Stahre, 1993

25 … Types of infiltration practices. Design methodologies are presented for three infiltration practices and two integrated (complementary) practices below: 1.Infiltration trenches 2.Infiltration basins 3.Bioretention area (and rain gardens) 4.Soil quality restoration 5.Native landscaping. Infiltration trench and infiltration basin systems rely directly on the site soil conditions to infiltrate the design capture volume of stormwater. Infiltration trenches and basins can be used on single/multi-family residential sites of up to 10 acres and up to 5 acres for commercial sites. Diunduh dari Sumber: ….. 17/10/2012

26 Diunduh dari Sumber: 17/10/2012 Slow the Flow: Manage and Reuse Storm Water On-Site …. Store and reuse stormwater beneficially: Soil amendment and infiltration is the most cost-effective way to store rainfall for landscape use Stormwater detention vaults/cisterns, if required, may be designed to feed filtration and reuse for toilet flushing or vehicle washing, or to store late spring storms for summer landscape irrigation.

27 Diunduh dari Sumber: ….. 17/10/2012 LAJU INFILTRASI …. Infiltration is the process by which water on the ground surface enters the soil. Infiltration rate in soil science is a measure of the rate at which soil is able to absorb rainfall or irrigation. It is measured in inches per hour or millimeters per hour. The rate at which water infiltrates into a ground is called the infiltration capacity.

28 When a soil is dry, the infiltration rate is usually high compared to when the soil is moist. For an initially dry soil subjected to rain, the infiltration capacity curve shows an exponentially decaying trend. The observed trend is due to the fact that when the soil is initially dry, the rate of infiltration is high but soon decreases, as most of the soil gets moist. The rate of infiltration reaches a uniform rate after some time. LAJU INFILTRASI …. Diunduh dari Sumber: ….. 17/10/2012

29 INDEKS INFILTRASI…. The average infiltration rate is called the Infiltration Index and the two types of indices commonly used are explained in the next section. Infiltration indices The two commonly used infiltration indices are : φ – index and W – index The φ - index : the rate of infiltration above which the rainfall volume equals runoff volume. The W – index This is the average infiltration rate during the time when the rainfall intensity exceeds the infiltration rate. Thus, W may be mathematically calculated by dividing the total infiltration (expressed as a depth of water) divided by the time during which the rainfall intensity exceeds the infiltration rate. Total infiltration may be fund out as under: Total infiltration = Total precipitation – Surface runoff – Effective storm retention The W – index can be derived from the observed rainfall and runoff data. It differs from the - index in that it excludes surface storage and retention. The index does not have any real physical significance when computed for a multiple complex watershed. Like the phi-index the - index, too is usually used for large watersheds. Diunduh dari Sumber: ….. 17/10/2012

30 Sumber: Pertanian Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012

31 Lansekap Pertanian Tekanan sosial dan ekonomi mengakibatkan fragmentasi dan fraksionasi lahan; ukuran individu persil semakin kecil, keaneka-ragaman dalam lansekap semakin besar Sumber: Pertanian Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012

32 Sumber: SMNO.hutanpinus.pujon.nop2012 Lansekap hutan tanaman industri dataran tinggi di DAS Konto

33 Peta Tutupan/Penggunaan Lahan DAS Sumber Brantas (2005) Sumber : Sudarto(2009) No data Sumber: Pertanian Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012

34 34 Land resources planning:Land resources planning: Communities Need Analysis Consumer Analysis & Participation Analysis Demand Analysis Priority Demand Land Suitability Analysis Land Capability Analysis Scenarios Feasibility Analysis Public Review Land Resources Allocation Decision Implementation, Monitoring, Evaluation, & Revision

35 Tutupan Lahan & Penggunaan Lahan di DAS Sumber Brantas Perhatikan hal-hal berikut dalam setiap macam tutupan lahan dan penggunaan lahan yang anda lihat di DAS Brantas Hulu : o Kanopi dan manajemen kanopi o Pengolahan tanah (guludan, parit, dsb) o Penutupan tanah (terbuka/tertutup) o Pemupukan o Pemberantasan Hama, Penyakit, Gulma o Irigasi dan/atau Drainasi o Pembuangan limbah/sampah Sumber: Pertanian Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012

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37 KEBERLANJUTAN USAHA PENANGANAN LAHAN KRITIS HASIL Usaha APA yang digarap ? (Lahan usaha) SIAPA YG berusaha (Masyarakat) Domestik Ekspor / Luar daerah Eksternal input KEBERDAYAAN

38 Siklus Air dalam Plot PRESIPITASI EVAPO- TRANSPIRASI INTERSEPSI LOLOS TAJUK LIMPASAN PERMUKAAN INFILTRASI PERKOLASI DRAINASI LATERAL Sumber: Pertanian Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012

39 Siklus Air dalam Plot ? Sumber: Pertanian Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012

40 Siklus Air dalam Plot Komponen Siklus Air (yang relevan) : Presipitasi (Hujan) Presipitasi (Hujan) Intersepsi (oleh tajuk tanaman) Intersepsi (oleh tajuk tanaman) Lolos Tajuk Lolos Tajuk Infiltrasi Infiltrasi Perkolasi Perkolasi Limpasan Permukaan Limpasan Permukaan Aliran Lateral (masuk dan keluar) Aliran Lateral (masuk dan keluar) Sumber: Pertanian Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012

41 Faktor yang berpengaruh terhadap besaran komponen siklus air di tingkat plotKomponen Siklus Air Faktor yang mempengaruhi besaran komponen Presipitasi(variabel bebas) Aliran Lateral 1) Kondisi Petak di bagian Hulu/Atas IntersepsiPenutupan Tajuk : Kerapatan Tajuk Tebal dan susunan Lapisan Tajuk (strata) Lolos Tajuk Intensitas dan durasi Hujan Kerapatan Tajuk InfiltrasiLaju Infiltrasi : Porositas (makro) Profil Tanah Intensitas Hujan dan Simpanan Permukaan PerkolasiPermeabilitas Tanah, Ketebalan Solum Evapotranspirasi 2) Ketersediaan air tanah, cuaca dan kondisi tanaman Limpasan Permukaan Resultante semua komponen Sumber: Pertanian Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012

42 Komponen Siklus Air Hutan Alam Hutan Tnm Pinus Kebun Apel Sayuran : Kentang Presipitasi100 Aliran Lateral Intersepsi Lolos Tajuk Infiltrasi Perkolasi Evapotrasnpirasi Limpasan Permukaan Komponen Siklus Air Hutan Alam Hutan Tnm Pinus Kebun Apel Sayuran : Kentang Presipitasi100 Aliran Lateral???? Intersepsi???? Lolos Tajuk???? Infiltrasi???? Perkolasi???? Evapotrasnpirasi???? Limpasan Permukaan???? DISKUSI Estimasi Neraca Air dalam Petak Tanaman saat terjadi hujan Diskusikan : Berapa proporsi masing-masing komponen ketika terjadi hujan 100 % Berapa proporsi masing-masing komponen ketika terjadi hujan 100 % Berapa besarnya limpasan permukaan dari berbagai macam penggunaan lahan ini Berapa besarnya limpasan permukaan dari berbagai macam penggunaan lahan ini Komponen Komponen apa saja yang berbeda? Mengapa demikian ? 1 ) Aliran lateral tergantung dari limpasan yang berasal dari petak dibagian hulu/atasnya 2 ) Evapotranspirasi sangat kecil (nol) karena durasi kejadian yang singkat dan cuaca hujan (kelembaban udara maksimum/jenuh) Sumber: Pertanian Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012

43 100% 50% 40% 10% Hujan (Presipitasi) Limpasan Permukaan Infiltrasi Evapo(transpi)rasi Contoh Neraca Air dari Kawasan Hutan/Pertanian Sumber: Pertanian Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012

44 Apa saja yang bisa terbawa keluar dari Plot bersama dengan aliran permukaan ? Material Tanah (sedimen) Material Tanah (sedimen) Bahan Organik : Bahan Organik : Pupuk Kandang (manure) Pupuk Kandang (manure) Kompos Kompos Sampah, seresah Sampah, seresah Unsur-unsur kimia : Unsur-unsur kimia : Unsur Hara Unsur Hara Pupuk Pupuk Pestisida, Herbisida, dsb Pestisida, Herbisida, dsb Lainnya ? Lainnya ?  Kondisi seperti apa yang bisa mendorong terangkutnya bahan 2 tsb bersama limpasan permukaan ? Sumber: Pertanian Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012

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46 PETAK dan LANSEKAP Apakah hal-hal yang terjadi dalam petak akan sama dengan yang terjadi di lansekap ? 1.Debit sungai merupakan akumulasi limpasan permukaan dari semua petak pertanian dan non pertanian dalam lansekap 2.Jumlah sedimen yang terangkut sungai merupakan akumulasi dari erosi dari seluruh petak dalam lansekap Sumber: Pertanian Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012

47 Apakah hal-hal yang terjadi di tingkat petak akan sama dengan di tingkat Lansekap ? IndikatorKemungkinan 1Kemungkinan 2 Limpasan Permukaan dan Debit Debit Banjir di sungai lebih besar dari jumlah semua limpasan yang keluar dari setiap petak dalam DAS Debit Banjir di sungai lebih kecil dari jumlah semua limpasan yang keluar dari setiap plot (petak) dalam DAS Erosi dan Sedimen Jumlah Sedimen yang terangkut di sungai lebih besar dari jumlah erosi (kehilangan tanah) dari setiap petak dalam DAS Jumlah sedimen yang terangkut di sungai lebih kecil dari jumlah erosi (kehilangan tanah) dari setiap petak dalam DAS Fungsi Lansekap (DAS) DAS atau lansekap tidak memiliki fungsi menahan (buffer) dan menyaring (filter). DAS atau lansekap mempunyai fungsi menahan (buffer) dan menyaring (filter). Pertimbangkan Longsor tebing sungai dan jalanLimpasan dari jalan dan pemukiman Sumber: Pertanian Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012

48 Adanya strip filter atau buffer sepanjang bantaran/sempadan sungai bisa mengurangi jumlah sedimen yang bisa masuk ke sungai, sehingga air sungai bisa tetap jernih Adanya cekungan alami (embung) dan relief mikro menjadi tempat singgah air permukaan sehingga tidak langsung mengalir ke sungai, meningkatkan kapasitas infiltrasi kawasan dan mengendapkan bahan terangkut air (sedimen dsb) Sumber: Pertanian Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012

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50 Debit Banjir (tahunan) Jumlah Sedimen Terangkut Debit dasar (tahunan) Dimodifikasi dari sumber : Susswein, van Noordwijk and Verbist (2002) Sumber: Pertanian Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012

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52 Sumber: Department of Agriculture Extension and Rural Sociology Institute of Agriculture and Animal Science Rampur, Chitwan, Nepal A Review on Organic Farming for Sustainable Agriculture Ananata Ghimire. June, 2002 Organic farming seems to be more appropriate as it considered the important aspects like sustainable. Agriculture is the most important sector for ensuring food security, alleviating poverty and conserving the vital natural resources that the world’s present and future generation will be entirely dependent upon for their survival and well being, in the name of development, the environmental resources have been beyond comprehension. Acid rain, deforestation, depletion, smog due to automobiles and discharge of industrial pollution, soil degradation, depletion of ozone layer and discharge of toxic wastage by industrial units into rivers and oceans are some environmental problematic issues. Intensive use of inorganic fertilizers and pesticides has been an important tool in the drive for increased crop production. In fact more fertilizers consumption is a good indication of agricultural productivity but depletion of soil fertility is commonly observed in soils. Due to heavy use of chemical herbicides, pesticides and intensification of agricultural production during the past few decades has led to other harmful effects like nitrate in the ground water, contamination of fooding materials, eutrophication, stratospheric changes etc. High agricultural inputs are unlikely to be sustainable for very long unless the inputs are correctly judged in terms of both their quality and quantity. To escape from these harmful effects, the concept of organic farming was emerged from the conference of Atlanta in Organic Farming seems to be more appropriate as it considered the important aspects like sustainable natural resources and environment. It is a production system, which favors maximum use of organic materials like crop residues, FYM, compost, green manure, oil cakes, bio-fertilizers, bio-gas slurry etc. to improve soil health from the different experiment, microbial fertilizers like Rhizomic, Azotobacter, Blue green algae, Azolla etc. have increased the yield and also played important role for minimizing the harmful effect of pesticides and herbicides. Organic farming is a practical proposition for sustainable agriculture if adequate attention is paid to this issue. There is urgent need to involve more and more scientist to identify the thrust area of research for the development of eco- friendly production technology.

53 Prinsip Pengelolaan di Tingkat Plot : 1 Sumber: Pertanian Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012

54 Prinsip Pengelolaan di Tingkat Plot : 2 Sumber: Pertanian Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012

55 BMPs : (Tanaman) Penutup Tanah diantara Barisan Tanaman Pokok Sumber: Pertanian Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012 Mulsa seresah tanaman di antara barisan tanaman jagung

56 Teknik Pengelolaan di tingkat lansekap : Sumber: Pertanian Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012

57 Teknik Pengelolaan di tingkat lansekap : Sumber: Pertanian Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012

58 Sumber : Bruno Verbist (2009)Penanaman yang rapat di sepanjang KAKISU (Sempadan Sungai) BAGAIMANA MERANCANG FILTER ATAU BUFFER ? Lembah Aliran Sungai Hutan Lindung Hutan Tanaman Pengendali Limpasan Kawasan Budidaya Sumber: Pertanian Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012

59 Manajemen pertanian terkait dengan kualitas air :  Praktek pertanian yang meningkatkan bahan organik dan biologi tanah  Praktek konservasi tanah dan air untuk mengendalikan limpasan dan erosi  Kombinasikan tanaman tahunan, semak, rumput dan tanaman semusim  Tanaman yang bisa menangkap unsur hara seperti penutup tanah  Kawasan penyangga antara lahan dengan tubuh air (sungai, danau, dsb)  Pengelolaan irigasi untuk menghindari pencucian hara  Mengintegrasikan ternak dalam sistem pertanian Sumber: Pertanian Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012

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61 Soemarno, …. Proses yg secara berkelanjutan mengoptimalkan manfaat SDL melalui penyerasian aktivitas ekonomi sesuai dg kapabilitas dan daya dukungnya Peningkatan Kesejahteraan MASYARAKAT Penghematan Konservasi Rehabilitasi PRODUKSI- DISTRIBUSI- KONSUMSI

62 Tidak ada tanah yang terbuka (bero) Tidak ada tanah yang terbuka (bero) Dalam selokan dan parit mengalir air yang jernih Dalam selokan dan parit mengalir air yang jernih Terdapat hewan/binatang liar sangat banyak Terdapat hewan/binatang liar sangat banyak Dijumpai ikan pada selokan dan sungai yang mengalir melalui lahan pertanian Dijumpai ikan pada selokan dan sungai yang mengalir melalui lahan pertanian Pada Lansekap Pertanian dijumpai aneka vegetasi (sangat beragam) Pada Lansekap Pertanian dijumpai aneka vegetasi (sangat beragam) Preston Sullivan, 2003 INDIKATOR LINGKUNGAN PERTANIAN SEHAT Sumber: Pertanian Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012

63 Kualitas hidup manusia di daerah miskin / kritis semakin menurun, indikatornya: Keterbatasa n income rumah- tangga Gizi Anak BALITA Penyakit akibat kesehatan lingkungan Kualitas Kawasan Konservasi/ Lindung Pudarnya Budaya- Kearifan Masyarakat

64 Contoh Indikator Fungsi Hidrologi DAS KarakteristikLokal Fungsi DAS (kriteria) Relevansi bagi pengguna Indikator Curah hujan Bentuk lahan Jenis tanah Kedalaman akar (dari vegetasi alami) KarakteristikLokal Fungsi DAS (kriteria) Relevansi bagi pengguna Indikator Curah hujan Bentuk lahan Jenis tanah Kedalaman akar (dari vegetasi alami) Transmisi airPengguna air di daerah hilirKetersediaan air sepanjang waktu (Sumber : Farida & Van Noordwijk, 2006) KarakteristikLokal Fungsi DAS (kriteria) Relevansi bagi pengguna Indikator Curah hujan Bentuk lahan Jenis tanah Kedalaman akar (dari vegetasi alami) Transmisi airPengguna air di daerah hilirKetersediaan air sepanjang waktu Menyangga pada kejadian puncak hujan Masyarakat yang tinggal di bantaran sungai dan bantaran banjir Tinggi muka air sampai batas terkendali Infiltrasi & melepaskan air secara bertahap Masyarakat yang tidak memiliki sistem penyimpanan air Sumur dangkal yang tidak kering Memelihara kualitas air Masyarakat yang tidak memiliki sistem purifikasi, PLTA Ketersediaan air bersih sepanjang waktu KarakteristikLokal Fungsi DAS (kriteria) Relevansi bagi pengguna Indikator Curah hujan Bentuk lahan Jenis tanah Kedalaman akar (dari vegetasi alami) Transmisi airPengguna air di daerah hilirKetersediaan air sepanjang waktu Menyangga pada kejadian puncak hujan Masyarakat yang tinggal di bantaran sungai dan bantaran banjir Tinggi muka air sampai batas terkendali Infiltrasi & melepaskan air secara bertahap Masyarakat yang tidak memiliki sistem penyimpanan air Sumur dangkal yang tidak kering Memelihara kualitas air Masyarakat yang tidak memiliki sistem purifikasi, PLTA Ketersediaan air bersih sepanjang waktu Mengurangi longsor Masyarakat yang tinggal di kaki bukit Intensitas kejadian longsor Mengurangi erosi Petani, Nelayan, PLTAKetebalan seresah & top- soil, biodiversitas ikan bioindikator bentos Mempertahankan iklim mikro Petani & wisatawanSuhu dan kelembaban Sumber: Pertanian Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012

65 Perubahan distribusi musiman aliran sungai di (A) DAS Kalikonto (Indonesia), dimana pada periode ke II ( ) terjadi alih guna hutan menjadi lahan pertanian dalam skala besar (sumber: Bruijnzeel, 1990) Contoh Indikator Fungsi Hidrologi DAS Kali Konto Sumber: Pertanian Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012

66 P ENCEMARAN DARI L AHAN P ERTANIAN Potensi Pencemar Air dari Lahan Pertanian : 1.Nitrogen 2.Pospor 3.Logam Berat 4.Kotoran Ternak (manure) 5.Pestisida 6.Patogen (penyebab penyakit pada Manusia) 7.Sedimen Pemberian Bahan Agrokimia (Pupuk dan Pestisida) dan Bahan Organik (Pupuk Kandang) yang berlebihan berpotensi menjadi potensi sumber pencemar Sumber: Pertanian Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012

67 Keuntungan yang diperoleh Pemilik Lahan (PETANI) Tambahan biaya yang ditanggung masyarakat (Kerugian MASYARAKAT) Kehilangan Air Bersih Kehilangan Biodiversitas Kehilangan Cadangan Karbon Penebangan Hutan dan Alih Fungsi Hutan ke Pertanian Pertanian dengan Upaya Konservasi Mandiri Pertanian dengan Upaya Konservasi Imbalan Jasa Diolah & dikembangkan dari : Pagiola (2003) Sumber: Pertanian Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012

68 W ATER QUALITY ? Foto2 : Kurniatun Hairiah Layanan Lingkungan : Mereka perlu air bersih Sumber: Pertanian Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012

69 Diunduh dari Sumber: ….. 17/10/2012 Need for drainage During heavy rainfall the upper soil layers become saturated and pools may form. Water percolates to deeper layers and infiltrates from the pools. Part of the water present in the saturated upper soil layers flows downward into deeper layers and is replaced by water infiltrating from the surface pools. When there is no more water left on the soil surface, the downward flow continues for a while and air re-enters in the pores of the soil. This soil is not saturated anymore.

70 Diunduh dari Sumber: ….. 17/10/2012 GROUNDWATER TABLE …. After heavy rainfall the groundwater table may rise and reach the rootzone The water flowing from the saturated soil downward to deeper layers, feeds the groundwater reservoir. As a result, the groundwater level (often called groundwater table or simply water table) rises. Following heavy rainfall or continuous over-irrigation, the groundwater table may even reach and saturate part of the rootzone. Again, if this situation lasts too long, the plants may suffer. Measures to control the rise of the water table are thus necessary. The removal of excess water either from the ground surface or from the rootzone, is called drainage.

71 Diunduh dari Sumber: ….. 17/10/2012 SOIL PROFILE …. A very general and simplified soil profile can be described as follows: a.The plough layer (20 to 30 cm thick): is rich in organic matter and contains many live roots. This layer is subject to land preparation (e.g. ploughing, harrowing etc.) and often has a dark colour (brown to black). b.The deep plough layer: contains much less organic matter and live roots. This layer is hardly affected by normal land preparation activities. The colour is lighter, often grey, and sometimes mottled with yellowish or reddish spots. c.The subsoil layer: hardly any organic matter or live roots are to be found. This layer is not very important for plant growth as only a few roots will reach it. d.The parent rock layer: consists of rock, from the degradation of which the soil was formed. This rock is sometimes called parent material.

72 Diunduh dari Sumber: ….. 17/10/2012 THE GROUNDWATER TABLE …. Part of the water applied to the soil surface drains below the rootzone and feeds deeper soil layers which are permanently saturated; the top of the saturated layer is called groundwater table or sometimes just water table.

73 Diunduh dari Sumber: ….. 17/10/2012 Perched groundwater table …. A perched groundwater layer can be found on top of an impermeable layer rather close to the surface (20 to 100 cm). It covers usually a limited area. The top of the perched water layer is called the perched groundwater table. The impermeable layer separates the perched groundwater layer from the more deeply located groundwater table

74 Diunduh dari Sumber: ….. 17/10/2012 Depth of the groundwater table …. The depth of the groundwater table varies greatly from place to place, mainly due to changes in topography of the area. In one particular place or field, the depth of the groundwater table may vary in time. Following heavy rainfall or irrigation, the groundwater table rises. It may even reach and saturate the rootzone. If prolonged, this situation can be disastrous for crops which cannot resist "wet feet" for a long period. The groundwater table can also be very deep and distant from the rootzone, for example following a prolonged dry period.

75 Diunduh dari Sumber: ….. 17/10/2012 HUJAN EFEKTIF…. Effective Rainfall When rain water ((1) in Fig. 63) falls on the soil surface, some of it infiltrates into the soil (2), some stagnates on the surface (3), while some flows over the surface as runoff (4). When the rainfall stops, some of the water stagnating on the surface (3) evaporates to the atmosphere (5), while the rest slowly infiltrates into the soil (6). From all the water that infiltrates into the soil ((2) and (6)), some percolates below the rootzone (7), while the rest remains stored in the rootzone (8). Effective rainfall (8) = (1) - (4) - (5) - (7)

76 Diunduh dari Sumber: ….. 17/10/2012 Effective rainfall and depth of the rootzone…. DEPTH OF THE ROOTZONE Soil water stored in deep layers can be used by the plants only when roots penetrate to that depth. The depth of root penetration is primarily dependent on the type of crop, but also on the type of soil. The thicker the rootzone, the more water available to the plant.

77 Diunduh dari Sumber: ….. 17/10/2012 Effective rainfall and topography…. Topography On steep sloping areas, because of high runoff, the water has less time to infiltrate than in rather flat areas. The effective rainfall is thus lower in sloping areas.

78 Diunduh dari Sumber: ….. 17/10/2012 Effective rainfall and initial soil moisture content…. Initial soil moisture content For a given soil, the infiltration rate is higher when the soil is dry than when it is moist. This means that for a rain shower occurring shortly after a previous shower or irrigation, the infiltration rate is lower and the surface runoff higher.. Effective rainfall and initial soil moisture content

79 Diunduh dari Sumber: conservation….. 17/10/2012 Maximizing Irrigation Efficiency and Water Conservation MAXIMIZE THE AMOUNT OF WATER ENTERING THE TURFGRASS ROOTZONE (STORAGE) BY: 1.controlling water movement below the root zone (leaching), 2.minimizing evaporative losses, 3.controlling surface water runoff and ponding of irrigation water.

80 Diunduh dari Sumber: adaptation/assessments/424….. 17/10/2012 Forest hydrological cycle (Hélie et al., 2005) ….

81 Diunduh dari Sumber: 17/10/2012 How much water do forests use? …. Trees and forests have the ability to use more water than shorter types of vegetation. In general, conifers lose between 25 to 45% of annual rainfall by interception, compared to 10 to 25% for broadleaves and almost 0% for grass. Conifers tend to lose an additional 300 mm to 350 mm per year due to transpiration, compared to 300 mm to 390 mm for broadleaves and 400 mm to 600 mm for grass.


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